1. Field of the Invention
The present invention relates to an intermediate shaft of a vehicle steering apparatus. More particularly, the present invention relates to an intermediate shaft of a vehicle steering apparatus that is capable of preventing foreign matter, for example, moisture, dust and oil, from being introduced into the intermediate shaft even from a process of transporting the intermediate shaft to assemble it to a vehicle, and even when the intermediate shaft is assembled to the vehicle and the vehicle is driven, so that a component of the intermediate shaft can be prevented from being deformed or damaged.
2. Description of the Prior Art
As generally known in the art, a vehicle steering apparatus is configured such that when a driver rotates a steering wheel in a desired direction, a steering shaft connected to the steering wheel is rotated, and an intermediate shaft transmits the rotatory force of the steering shaft to a gear box, which includes a rack and pinion gear, through a universal joint.
In that event, the gear box converts the rotational motion of the steering shaft into a rectilinear motion by the rack and pinion gear, and transmits the rectilinear motion to a rack bar. The rack bar transmits the force to a tie rod connected to a tire knuckle such that the driving direction of the vehicle can be changed.
In particular, the axis between steering shaft and the gear box is configured by an input shaft and an output shaft which are angled to each other rather than being coaxially aligned, which makes it difficult to transmit power with a conventional shaft coupling method. Therefore, it is essential to employ an intermediate shaft and a universal joint so as to make the angle of the steering shaft variable within a predetermined range.
FIG. 1 is a schematic view of a vehicle steering apparatus that employs a conventional intermediate shaft.
As illustrated in FIG. 1, in a conventional vehicle steering apparatus, the lower end of a steering shaft 130 is connected with a gear box 180. However, because the steering shaft 130 is adapted to be connected with the gear box 180 in a state where the steering shaft 130 is inclined by a predetermined angle due to the circumstances thereof, an intermediate shaft 100 is used to meet with such a condition.
Here, the term, “intermediate shaft,” is used to collectively refer to a member configured by, for example, a universal joint 110, an outer member 122, and an inner member 124 to transmit a rotatory force even in a state where it is curved by a predetermined angle.
The intermediate shaft 100 is an apparatus that is connected, at one end thereof, to the steering shaft 130 joined with a steering wheel 170, and, at the other end, to the gear box 180 such that the rotatory force produced in the steering wheel 170 can be transmitted to vehicle wheels through the gear box 180.
A steering column 150 includes an outer tube 145, an inner tube 140, and a mounting bracket 160. The outer tube 145 is formed in the steering wheel 170 side, and the inner tube is provided in the outer tube 145. Because the inner tube 140 has a diameter smaller than that of the outer tube 145, the inner tube 140 can be introduced into the outer tube 145 when an impact is applied thereto. Because each of the outer tube 145 and the inner tube 140 is formed in a hollow tube type, the steering shaft 130 can be smoothly rotated.
In order for the intermediate shaft 100 to be capable of transmitting the rotatory force even in a state where it is curved by a predetermined angle, the universal joint 110 is mounted at each end of the intermediate shaft 100 such that the rotatory force transmitted from one universal joint 110 mounted at one end can be transmitted to the other universal joint 110.
However, such a conventional intermediate shaft of a vehicle steering apparatus has a problem in that foreign matter, for example, moisture, dust and oil, is introduced into the inside of the intermediate shaft not only in the process of transporting the intermediate shaft to assemble it to a vehicle but also even when the intermediate shaft is assembled to the vehicle and the vehicle is driven, thereby causing a component to be deformed or damaged.
In addition, the deformation and damage of the intermediate shaft may be led to inability of steering or poor steering while the vehicle is being driven. As a result, a fatal problem may occur that causes a safety accident.